Temperature sensor for micro-controller using an NTC thermistor

Temperature sensor for Micro-controllers

This temperature sensor is used for micro-controllers to measure a range of temperatures. This sensor uses the
( NCPppXH103) NTC surface mount thermistor. You can use any thermistor, but you must have the datasheet for that specific thermistor to get the thermistor resistance ratio in order for your micro-controller to be able to calculate the voltage into a temperature unit. This circuit above is basically a variable voltage divider, where the voltage on the output changes depending on the temperature. There is a ratio between the temperature and the resistance of the thermistor. This is how the micro-controller can calculate the temperature. The voltage that comes out from the output goes out to the ADC in the micro-controller. This sensor can be used with an Arduino or an Atmega chip or other micro-controller.

On the above left i have the surface mount thermistor on a piece of perf board which can be detached from my micro-controller.
In a later post i will show you how to make your own microcontoller and show the specs of my microcontoller.
On the left you can see the senor detached.
I have used the sensor, and its pretty accurate, but you have to do trial and error with the code. Stay tuned for the code with the sensor, where it can display the temperature on to a LCD display, but the this code is used with an Atmega chip and programmed with an Atmel Studio. I will post the code with arduino, later on.

Using ohms law

An easy way to remember ohms law ( the orientation of voltage, current and resistance) is the ohms law triangle.  Below is what the triangle looks like:

V=Voltage, I=Current, R=Resistance

Just remember V over I equals R.
This triangle can help you remember ohms law and make it easier to calculate each value.
Ohms law states the potential difference (voltage) across a conductor is proportional to the current flowing through the conductor.
To calculate ohms law in a circuit with the triangle, you would cover the variable that you want to find and input the other 2 variable and calculate, either multiply or divide. You divide the numbers when one is on top of the other like V/I or V/R. You multiply when the numbers are beside each other like I*R.

For example:
To calculate R, you'd cover R and you'd have V/I, so input the voltage and current from the circuit and divide to get the resistance.
To Calculate I, you'd cover I  and you'd have V/R, so you input  the voltage and current from the circuit and divide voltage by current.
To calculate V, you'd cover V and you'd have I*R, so you input the current and resistance from the circuit and multiply current (I) by resistance (R).

How to read Surface Mount resistor

To read and calculate a SMD resistor, you must find out what code the resistor is using, in order to calculate it. There are 3 categories which are shown below:

Has an R,K or M between the numbers                                                                        

To calculate a 3 digit code resistance, Find the 3 digit code on the resistor, the first and second numbers are the significant number/ first 2 digit of resistance, the 3rd digit is the multiplier. The multiplier is an exponent of 10, so on the left you see i have 131, so the first 2 digits is 1,3 and the multiplier is 1 which is 10^1. To calculate the resistance, you multiply 13 by 10^1 which is 13 x 10^1 =130 ohms. So the resistors resistance is 130 ohms.

To calculate a 4 digit code resistance, locate the 4 digit code on the resister. The first, second and third number on the resistor are the significant number/ first 3 digits of the resistance  and the 4th number is the multiplier. The multiplier is an exponent of 10 , so on the left i have a resister with a code of 4450, so the first 3 digits are 4,4,5 and the multiplier is zero which is 10^0. To calculate the resistance multiply 445 by 10^0 which is 445 x 10^0 =445 ohms. So the resistors resistance is 445 ohms.

To calculate a resistor with a Radix point. Locate the 3 or 4 digit code with an R,K or M in the middle. The letters act as a decimal, so you just replace the location of the letter with a decimal point. In this resistance code, there is no multiplier. The letters also represent the unit of the resistance in the resistor so R represents ohms, K represents kilo-ohms and M represents mega-ohms.  For example on the left i have 45R3, so you replace R with a decimal which would look like 45.3 and since R is ohms, the resistance is 45.3 ohms. Another example is 4k3 which would be 4.3k. Another example is R33 which would be .33 ohms.

How to read color coded resistor values

4 Banded resistor

Reading color banded resistor values
This post shows how to read a resistors value by using the chart above. I don't recommend just using this chart to only calculate the resistance of a resistor, I suggest using a multimeter to double check or to check the resister's values. To calculate the value, first locate the first band, it is in the area where the colors bands are closer together like seen on the left picture. The first band of the color band cluster is the first band.
Start calculating the value by matching the first and second or third (three bands if the resistor is a 5 banded resistor) band colors to the chart, the numbers you get are the first 2 or 3 digits or the significant numbers. then find the 3rd or 4rth (4rth band for 5 banded resistor) band color in the chart in the multiplier column. The number you get is the multiplier,  you would multiply the first 2 or 3 digits by the multiplier to get the resistance value. For the fourth or fifth (fifth band for five banded resistor) band, it is not really needed, but after you match the color with the number, it tell you how accurate, the resistance is of the resistor.
Look below at how I find the resistance:

Reading binary (from binary to decimal)

To read binary, you need to convert the binary number into expanded exponential form but instead of using 10 as the base each time, you would use 2.
For example, (normal way) using 10 as the base it would look like: 1011=1x10^3 + 0x10^2 + 1x10^1 + 1x10^0.

But to convert 1011 from binary to decimal you would do what i did at the bottom which i replaced the 10 as twos,  calculate each exponent and multiplying each exponent by the binary number that they are assigned to. After you add the numbers together to get the decimal number from binary.
For Example 1011 =1x2^3 + 0x2^2 + 1x2^1 + 1x2^0
                               =8         +  0        + 2         +  1
                               =11
So 1011 would equal 11.

Below, the chart might help you understand how to convert binary to number.

Calculating capacitance of non-polarized capacitors

Calculating non  polarized capacitor capacitance
To calculate the capacitance of a non polarized capacitor, locate the 3 digit code like on the picture on the left (locate the 3 numbers that are alongside each other).  The use the chart above to figure out the capacitance. The first and second number of the 3 digit code are the first 2 digits. The third number of the code shows multiplier which you would find in the chart, find the multiplier number and multiply the first 2 digits by the multiplier to get the capacitance. The capacitance calculated is in Pico-farads (pF). To convert the pf to another capacitance unit, use the chart below.